Colorectal cancer (CRC), the second leading cause of cancer mortality in the United States, is preventable and curable when found in its early stages. Although several chemopreventive agents prevent CRC in experimental animal models, no agent has been approved for human use. Besides surgical resection, which is rarely curative in advanced disease, current therapy for colon cancer relies on traditional cytotoxic agents with limited effects. Our long-term goal is to develop modified oligonucleotides (ODNs) to provide innovative therapeutic products for the treatment of cancer, in particular CRC. The formation of a transcriptional complex between an oncogenic beta-catenin and a T cell factor (TCF) is believed to be a key event in CRC cell development. Agents that modulate this pathway and/or disrupt the beta-catenin and TCF interaction are likely to inhibit the subsequent expression of many target genes that leads to CRC. The goal of this project is to identify a tight-binding and highly specific ODN that will bind to the beta-catenin binding domain of human TCF4 (TCF-CBD) to block the beta-catenin binding with TCF and/or disrupt the beta-catenin and TCF interaction. Structure-based design and novel combinatorial selection will be used to achieve this goal. Three specific aims will be pursued: Aim (1) express, purify, and characterize the TCF-CBD protein; Aim (2) identify tightly binding and highly specific aptamers containing 5-aminoallyl-2'-deoxyuridine (5-AA-aptamers) targeting TCF-CBD; Aim (3) test the 5-AA-aptamers for disruption of the beta-catenin.TCF complex in vitro. These experiments should ultimately introduce new lead anti-CRC compounds. Such lead compounds will be tested in cell cultures and animal models. Our novel anticancer discovery and development strategy can be applied to other cancers. In addition, the results generated from this research will be used in an application for a future NIH RO1 grant. Lay abstract: Development of anticancer drugs has proven to be challenging. However, oligonucleotide- based inhibition drugs can be selected from a very large random pool (10[12] approximately 10[14] members) by their ability to bind a specific protein. This novel anticancer strategy is important because it should allow us to very rapidly discover highly effective drug compounds. [unreadable] [unreadable] [unreadable]